The present invention relates to an improvement in a keyboard, particularly to the utilization of the light-emitting effect of light-emitting diodes which are mounted under transparent keys of the keyboard. The user is thus able to telephone at night or in darkness without the help of any other illumination. The symbols and the legends of the keys can be clearly seen with the help of the light emitted by the light-emitting diodes only when the handset of the telephone set is picked up or only when the switch is turned on.
Owing to the advance of civilization, human beings want to use time effectively in order to reach the highest working efficiency. The telephone is designed for the urgent need of human beings. Thus, the telephone has become an indispensable communicating device of every family and company. There is, however, often a problem particularly when telephoning somebody in darkness or in a car, because the keys or symbols cannot be seen clearly. Thus, it is necessary to have another light-emitting device in order to telephone in darkness, and extra effort must be made to switch on a lamp before telephoning. Considering that the matter described above often happens in the cold winter, it is a very annoying problem. Although, there is a light-emiting device using a bulb or a fluorescent tube, it occupies a large part of the keyboard and only indicates the line being used, and it is easily burned out.
The primary object of the present invention is to provide a light-emitting device mounted under the keys of a keyboard, which emits light by using light-emitting diodes, so that the user may easily distinguish the symbols on the keys in a dark place or in darkness by means of the light emitted by the light-emitting device without any other illuminative device. Thus, the user can telephone directly and immediately. The object of practicality is thus, accomplished.
Another object of the present invention is to provide a light-emitting device mounted on the keys of a keyboard in which the switch of the handset is used for connecting the light-emitting diode in series, so that the circuit of the light-emitting diodes are cut off automatically when the switch is turned off when the handset is placed on the telephone set. The object of convenience is thus, accomplished.
Still another object of the present invention is to provide a novel light-emitting device mounted under the keys of a keyboard. The device is bonded on a PC board and is protected by being covered with epoxy resin which prolongs the life of the device and prevents damage. In particular, the present device does not occupy much space inside the keys and since the keyboard can be made as an extremely thin profile, the cost is decreased. The object of economy is thus, accomplished.
A further object of the present invention is to provide a novel light-emitting device mounted under the keys of a keyboard and is characterized in that the light emitted by the light-emitting device passes through an elastic actuator which consists of a conductive rubber pad contact element and an insulated elastic rubber dome sheet to the transparent keys. The keys also function to protect the light-emitting diode from pressure contact when the key is pushed.